Locomotion in all animal species relies on precise coordination: animals must synchronize a myriad of muscle flexion and extension events in a stereotyped and rhythmic manner. At the core of motor coordination are central pattern generators (CPGs), neural circuits that have the capacity to produce rhythmic outputs from relatively simple, non-rhythmic inputs. Although there exists a large amount of functional evidence for both locomotor and non-locomotor CPGs, the cellular components of CPGs that mediate coordinated locomotion in more complex systems remain largely undefined. Further, how locomotor CPG activities are integrated with each other and modified by descending and sensory inputs is also largely unknown at the cellular level. These gaps in our knowledge may be due not only to the complexity of the neural circuitry, but also a consequence of the complexity of the behaviors under investigation. To address these challenges, the long-term goal for this project is to complement and expand upon existing efforts in other systems to characterize locomotor neural circuits using the powerful genetic tools available in the fruit fly, Drosophila melanogaster. In this proposal, a novel, high-resolution assay that quantitatively measures dozens of walking parameters in the fruit fly model will be used to screen for specific mutant phenotypes that occur as a consequence of activating and/or suppressing neural activity in subsets of neurons. Follow-up experiments are proposed to identify the neurons that are responsible for these mutant phenotypes.